/*
 *    Copyright 2009-2014 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.builder.xml;

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

import org.apache.ibatis.io.Resources;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

/**
 * Offline entity resolver for the MyBatis DTDs
 * 
 * @author Clinton Begin
 */
public class XMLMapperEntityResolver implements EntityResolver {

	private static final Map<String, String> doctypeMap = new HashMap<String, String>();

	private static final String IBATIS_CONFIG_PUBLIC = "-//ibatis.apache.org//DTD Config 3.0//EN".toUpperCase(Locale.ENGLISH);
	private static final String IBATIS_CONFIG_SYSTEM = "http://ibatis.apache.org/dtd/ibatis-3-config.dtd".toUpperCase(Locale.ENGLISH);

	private static final String IBATIS_MAPPER_PUBLIC = "-//ibatis.apache.org//DTD Mapper 3.0//EN".toUpperCase(Locale.ENGLISH);
	private static final String IBATIS_MAPPER_SYSTEM = "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd".toUpperCase(Locale.ENGLISH);

	private static final String MYBATIS_CONFIG_PUBLIC = "-//mybatis.org//DTD Config 3.0//EN".toUpperCase(Locale.ENGLISH);
	private static final String MYBATIS_CONFIG_SYSTEM = "http://mybatis.org/dtd/mybatis-3-config.dtd".toUpperCase(Locale.ENGLISH);

	private static final String MYBATIS_MAPPER_PUBLIC = "-//mybatis.org//DTD Mapper 3.0//EN".toUpperCase(Locale.ENGLISH);
	private static final String MYBATIS_MAPPER_SYSTEM = "http://mybatis.org/dtd/mybatis-3-mapper.dtd".toUpperCase(Locale.ENGLISH);

	private static final String MYBATIS_CONFIG_DTD = "org/apache/ibatis/builder/xml/mybatis-3-config.dtd";
	private static final String MYBATIS_MAPPER_DTD = "org/apache/ibatis/builder/xml/mybatis-3-mapper.dtd";

	static {
		doctypeMap.put(IBATIS_CONFIG_SYSTEM, MYBATIS_CONFIG_DTD);
		doctypeMap.put(IBATIS_CONFIG_PUBLIC, MYBATIS_CONFIG_DTD);

		doctypeMap.put(IBATIS_MAPPER_SYSTEM, MYBATIS_MAPPER_DTD);
		doctypeMap.put(IBATIS_MAPPER_PUBLIC, MYBATIS_MAPPER_DTD);

		doctypeMap.put(MYBATIS_CONFIG_SYSTEM, MYBATIS_CONFIG_DTD);
		doctypeMap.put(MYBATIS_CONFIG_PUBLIC, MYBATIS_CONFIG_DTD);

		doctypeMap.put(MYBATIS_MAPPER_SYSTEM, MYBATIS_MAPPER_DTD);
		doctypeMap.put(MYBATIS_MAPPER_PUBLIC, MYBATIS_MAPPER_DTD);
	}

	/*
	 * Converts a public DTD into a local one
	 * 
	 * @param publicId The public id that is what comes after "PUBLIC"
	 * 
	 * @param systemId The system id that is what comes after the public id.
	 * 
	 * @return The InputSource for the DTD
	 * 
	 * @throws org.xml.sax.SAXException If anything goes wrong
	 */
	public InputSource resolveEntity(String publicId, String systemId) throws SAXException {

		if (publicId != null)
			publicId = publicId.toUpperCase(Locale.ENGLISH);
		if (systemId != null)
			systemId = systemId.toUpperCase(Locale.ENGLISH);

		InputSource source = null;
		try {
			String path = doctypeMap.get(publicId);
			source = getInputSource(path, source);
			if (source == null) {
				path = doctypeMap.get(systemId);
				source = getInputSource(path, source);
			}
		} catch (Exception e) {
			throw new SAXException(e.toString());
		}
		return source;
	}

	private InputSource getInputSource(String path, InputSource source) {
		if (path != null) {
			InputStream in;
			try {
				in = Resources.getResourceAsStream(path);
				source = new InputSource(in);
			} catch (IOException e) {
				// ignore, null is ok
			}
		}
		return source;
	}

}